JP2009191346A - Surface treatment agent, surface treatment method, and surface-treated carbon steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment agent containing no phosphor, and to provide a surface treatment method using the surface treatment agent containing no phosphor. <P>SOLUTION: The surface treatment agent is formed of an aqueous solution which contains one or more organic chelating agents selected from aminocarboxylic acids and aminocarboxylates, and in which the concentration of the organic chelating agents is adjusted to 1 g/L to 300 g/L, and the pH is 4.0 to 9.0. The surface treatment method includes the steps of: immersing carbon steel into a treatment liquid in which Fe<SP>2+</SP>is added to the surface treatment agent formed of the aqueous solution that contains one or more organic chelating agents selected from the aminocarboxylic acids and the aminocarboxylates; and adjusting the pH of the treatment liquid, the concentration of the organic chelating agent in the treatment liquid, the concentration of Fe<SP>2+</SP>in the treatment liquid, the concentration of Fe<SP>3+</SP>in the treatment liquid, and the oxidation-reduction potential of the treatment liquid. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface treatment agent and a surface treatment method for carbon steel, and a surface-treated carbon steel.

  As a pretreatment for the wire drawing process of the steel wire made of carbon steel, washing is performed with hydrochloric acid or sulfuric acid in order to remove the oxide scale on the surface of the steel wire, and further washing with water to remove the acid. Thereafter, a lubricating film is formed on the surface of the steel wire. Although these treatments are performed continuously, the surface of the steel wire immediately after the acid cleaning becomes activated, and water rust is generated on the surface after the water cleaning. Water rust remains on the surface of the wire during the coating treatment, and the treated coating is colored brown. As a result, the steel wire after the wire drawing treatment is also colored by water rust. Discoloration due to water rust on the surface of steel wires not only detracts from aesthetics and lowers the product value, but also shortens the die life during wire drawing and reduces productivity.

In patent document 1, the process using the smut removal liquid containing a phosphonate is performed after water washing, the smut (water rust) which generate | occur | produced after water washing is removed, and the quality of a product is improved.
Japanese Patent No. 3206636

  However, since the smut removing liquid of Patent Document 1 contains phosphorus, delayed breakage of the steel wire due to immersion phosphorus occurred after the treatment. In addition, it has been a problem that waste liquid treatment is difficult. Considering the influence of phosphorus immersion and waste liquid treatment, it is preferable that the surface treatment agent for carbon steel does not contain phosphorus. Therefore, it has been desired to develop a surface treatment agent that has the same effect as a phosphorus-containing surface treatment agent and that does not contain phosphorus.

  This invention is made | formed in order to solve the said subject, Comprising: The surface treatment method which uses the surface treatment agent which does not contain phosphorus, and the surface treatment agent which does not contain phosphorus is provided.

  In order to solve the above problems, the present invention contains one or more organic chelating agents selected from aminocarboxylic acids and aminocarboxylic acid salts, and the concentration of the organic chelating agent is 1 g / L or more and 300 g / L or less. And a surface treating agent comprising an aqueous solution having a pH adjusted to 4.0 or more and 9.0 or less.

  The surface treating agent of the present invention uses an organic chelating agent that does not contain phosphorus as an effective agent. Therefore, it is possible to prevent delayed destruction due to immersion phosphorus after processing. Moreover, since waste liquid processing becomes easy, handling becomes easy compared with the conventional phosphorus containing water processing agent.

  When the concentration of the organic chelating agent is less than 1 g / L, the surface treatment capability such as removal of water rust is insufficient, and when it is higher than 300 g / L, the carbon steel surface is excessively dissolved. Therefore, the organic chelating agent concentration is 1 g / L or more and 300 g / L or less, preferably 5 g / L or more and 200 g / L or less, more preferably 10 g / L or more and 100 g / L or less.

  Further, if the pH of the aqueous solution is less than 4.0, an oxide scale is generated on the surface of the carbon steel after the surface treatment. When the pH of the aqueous solution exceeds 9.0, the surface treatment ability decreases. If pH is the range of 4.0 or more and 9.0 or less, it can be set as the surface treating agent which has high surface treatment capability. The pH range is preferably 4.5 or more and 8.5 or less, more preferably 4.8 or more and 8.0 or less.

  In the above invention, the aqueous solution preferably contains a surfactant or a glycol solvent. The effect of suppressing the generation of oxide scale on the surface of the carbon steel after the surface treatment is obtained by the surfactant or the glycol solvent.

Further, the present invention immerses carbon steel in a treatment liquid in which Fe ²⁺ is added to a surface treatment agent comprising an aqueous solution containing one or more organic chelating agents selected from aminocarboxylic acids and aminocarboxylates. The process, the pH of the treatment liquid, the concentration of the organic chelating agent in the treatment liquid, the concentration of Fe ^{2+ in} the treatment liquid, the Fe ³⁺ concentration in the treatment liquid, and the oxidation of the treatment liquid And a step of adjusting the reduction potential.

By using a treatment liquid in which Fe ²⁺ is added to a surface treatment agent containing an organic chelating agent, the oxidation-reduction potential of the treatment liquid can be lowered and the surface treatment ability can be improved. While adjusting the pH of the treatment liquid, the concentration of the organic chelating agent in the treatment liquid, the concentration of Fe ^{2+ in} the treatment liquid, the Fe ³⁺ concentration generated by the surface treatment, and the oxidation-reduction potential of the treatment liquid, By treating the surface, the surface treatment capability can be increased. Moreover, when making an iron and steel wire into a process target, the bad influence on the wire drawing property by the overmelting of the wire surface can be suppressed.

  In this case, it is preferable to adjust the pH of the treatment liquid to a range of 4.0 or more and 9.0 or less.

  When the pH of the treatment liquid is less than 4.0, an oxide scale is generated on the surface of the carbon steel after the surface treatment. When the pH exceeds 9.0, the surface treatment ability decreases. Moreover, when surface-treating a steel wire, the water rust removed by surface treatment precipitates as iron hydroxide. If the pH of the treatment liquid is 4.0 or more and 9.0 or less, preferably 4.5 or more and 8.5 or less, more preferably 4.8 or more and 8.0 or less, the surface treatment ability can be improved. In addition, the generation of oxide scale after the surface treatment can be prevented.

  In this case, it is preferable to adjust the concentration of the organic chelating agent to a range of 1 g / L to 300 g / L.

  When the concentration of the organic chelating agent in the treatment liquid is less than 1 g / L, the surface treatment ability is insufficient. When the concentration of the organic chelating agent is higher than 300 g / L, the carbon steel surface is excessively dissolved. When a steel wire is processed, the wire drawing after the surface treatment is adversely affected. By adjusting the organic chelating agent concentration in the treatment liquid to a range of 1 g / L to 300 g / L, preferably 5 g / L to 200 g / L, more preferably 10 g / L to 100 g / L. The surface treatment ability of the liquid can be increased, and good physical properties can be imparted to the treated carbon steel.

In this case, the Fe ²⁺ concentration is preferably adjusted to 10 mg / L or more. When the Fe ²⁺ concentration in the treatment liquid is less than 10 mg / L, the oxidation-reduction potential becomes high and the reduction power becomes weak, so that the surface treatment ability is lowered. Therefore, the Fe ²⁺ concentration is adjusted to 10 mg / L or more, preferably 30 mg / L or more, more preferably 50 mg / L or more.

In this case, it is preferable to adjust the Fe ³⁺ concentration to 1000 mg / L or less. When the surface treatment proceeds, for example, water rust on the surface of the steel wire is dissolved in the treatment liquid, thereby increasing Fe ³⁺ . When the concentration of Fe ³⁺ exceeds 1000 mg / L, the oxidation-reduction potential increases due to the oxidation action of Fe ³⁺ and the reducing power becomes weak, so that the surface treatment ability decreases. Moreover, the ingot of carbon steel is corroded by the oxidizing action of Fe ³⁺ . For this reason, in the case of a steel wire rod, the problem that the frequency | count of disconnection at the time of wire drawing increases significantly arises.

  In this case, the oxidation-reduction potential is preferably adjusted to 510 mV or less with respect to the hydrogen standard electrode potential. The oxidation-reduction potential of the treatment liquid is a parameter that affects the surface treatment ability and the corrosivity of the carbon steel ingot. In an oxidizing atmosphere, the surface treatment capability is insufficient, and the amount of metal corrosion due to oxidation increases. When the oxidation-reduction potential is 510 mV or less, preferably 460 mV or less, more preferably 410 mV or less with respect to the hydrogen standard electrode potential, the surface treatment ability is improved, and corrosion of the metal can be prevented.

  In the above invention, the aqueous solution may contain a surfactant or a glycol solvent. When the time from the surface treatment process to the next process (for example, the film treatment process) is long, an oxide scale is generated on the surface of the carbon steel after the surface treatment. By further containing a surfactant or glycol solvent in the surface treatment agent, the rust prevention performance after the surface treatment can be further improved.

Further, the present invention is immersed in a treatment solution obtained by adding Fe ²⁺ to an aqueous solution containing one or more organic chelating agents selected from aminocarboxylic acids and aminocarboxylates, and the pH of the treatment solution and the treatment The surface was treated by adjusting the concentration of the organic chelating agent in the liquid, the concentration of Fe ^{2+ in} the treatment liquid, the Fe ³⁺ concentration in the treatment liquid, and the oxidation-reduction potential of the treatment liquid. Provide carbon steel.

  The carbon steel treated by the above process is reliably subjected to surface treatment, and generation of oxidized scale after the treatment is suppressed. Therefore, it is excellent in aesthetics. For example, in the case of a steel wire rod, damage to the die can be reduced at the time of wire drawing and the die life can be extended, corrosion of the metal can be reduced, and the number of wire breaks at the time of wire drawing can be greatly reduced.

According to the present invention, surface treatment can be performed without excessively dissolving the carbon steel surface. Moreover, generation | occurrence | production of the oxide scale after surface treatment can be suppressed. Since the surface treatment agent of the present invention does not contain phosphorus, delayed destruction due to phosphorus immersion does not occur, and waste liquid treatment is easy.
The carbon steel treated by the surface treatment agent and the surface treatment method of the present invention is excellent in aesthetics because the surface treatment is reliably performed and the generation of oxide scale after the surface treatment is also suppressed. For example, in a steel wire rod, damage to the die can be reduced at the time of wire drawing, and the die life can be extended. Corrosion of the metal can be reduced and the number of wire breaks during wire drawing can be greatly reduced.

Below, the case where the water rust of the steel wire rod made of carbon steel is removed is taken as an example, and the surface treatment agent and the surface treatment method according to the present invention will be described.
A steel wire made of carbon steel is pre-treated in the order of an acid washing step, a water washing step, a water rust removal step, and a surface film treatment step, and then drawn in a dry drawing step.

<Acid cleaning process>
In the acid cleaning step, hydrochloric acid or sulfuric acid is used to remove oxide scale (Fe ₂ O ₃ , Fe ₃ O ₄ , FeO) formed on the surface of the wire. The acid concentration, the treatment temperature, the treatment time, and the iron concentration in the liquid are determined in consideration of the ability to remove oxide scale, the degree of corrosion of the bare metal of the wire, the treatment efficiency, and the like. For example, acid cleaning is performed under the conditions shown in Table 1.
The acid cleaning treatment may be performed in a single tank or a multistage system using a plurality of tanks.

<Washing process>
After the acid cleaning, water washing is performed to remove the acid attached to the wire. The water washing step can be performed by a multistage water tank or a shower.

<Water rust removal process>
In the water rust removal step, rust (water rust) generated after acid cleaning is removed.
The surface treatment agent of this embodiment consists of an aqueous solution containing one or more organic chelating agents selected from aminocarboxylic acids and aminocarboxylates. Specific examples of the aminocarboxylic acid include nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and triethylenetetraminehexaacetic acid. Examples of aminocarboxylic acid salts include sodium salts, potassium salts, lithium salts, ammonium salts, amine salts, and alkanolamine salts of aminocarboxylic acids described above.

  The concentration of the organic chelating agent is 1 g / L or more and 300 g / L or less, preferably 5 g / L or more and 200 g / L or less, more preferably 10 g / L or more and 100 g / L or less.

  The pH is 4.0 or more and 9.0 or less, preferably 4.5 or more and 8.5 or less, and more preferably 4.8 or more and 8.0 or less. In order to adjust the pH, an acid such as hydrochloric acid, sulfuric acid, nitric acid or acetic acid, or an alkali such as monoethanolamine, diethanolamine, triethanolamine, sodium hydroxide or potassium hydroxide is added to the surface treatment agent.

In order to promote removal of water rust, a reducing agent can be added to the surface treatment agent. Specific examples of the reducing agent include ascorbic acid, erythorbic acid, tartaric acid, oxalic acid, citric acid, malic acid, and salts thereof, ferrous chloride (FeCl ₂ ), and ferrous sulfide (FeS).

  In order to suppress the generation of oxide scale after removal of water rust, a surfactant or glycol solvent may be added to the surface treatment agent. An example of a surfactant is sodium alkylaminopropionate. An example of the glycol solvent is propylene glycol.

In this embodiment, Fe < ²⁺ > is added with respect to said surface treating agent, and it is set as the processing liquid for water rust removal. By adding Fe ²⁺ , the oxidation-reduction potential of the treatment liquid is lowered and the water rust removal ability is improved. The concentration of Fe ²⁺ in the treatment liquid is 10 mg / L or more, preferably 30 mg / L or more, more preferably 50 mg / L or more. Fe ²⁺ can be added by dissolving ferrous chloride in the surface treatment agent. Or you may mix the processing liquid which the water rust removal capability fell and became unusable because the organic chelating agent density | concentration fell to an unused surface treating agent. In this case, since the processing liquid that has become unusable is reused, there are advantages that the processing cost can be reduced and the amount of waste liquid can be reduced.

The steel wire in which water rust is generated is immersed in the above-described processing liquid, and water rust removal processing is performed. During the water rust removal treatment, the pH of the treatment liquid, the concentration of the organic chelating agent in the treatment liquid, the Fe ²⁺ concentration, the Fe ³⁺ concentration, and the oxidation-reduction potential value of the treatment liquid are measured and managed.

  During the water rust removal treatment, the pH of the treatment liquid is adjusted in the range of 4.0 to 9.0, preferably 4.5 to 8.5, more preferably 4.8 to 8.0. The pH of the treatment liquid can be adjusted by adding the acid or alkali described above.

  The concentration of the organic chelating agent in the treatment liquid is 1 g / L or more and 300 g / L or less, preferably 5 g / L or more and 200 g / L or less, more preferably 10 g / L or more and 100 g / L or less. The concentration of the organic chelating agent is measured by capillary tube isotachophoresis, capillary electrophoresis, or titration. When the concentration of the organic chelating agent in the treatment liquid is less than 1 g / L, sufficient water rust removal cannot be performed, so the treatment liquid is replaced.

During the water rust removal treatment, the concentration of Fe ^{2+ in} the treatment liquid is adjusted to 10 mg / L or more, preferably 30 mg / L or more, more preferably 50 mg / L or more. When the Fe ²⁺ concentration becomes smaller than the above value, ferrous chloride or a treatment liquid that cannot be used is added. The Fe ²⁺ concentration is measured by, for example, a titration method using an ethylenediaminetetraacetic acid solution.

As the water rust removal treatment proceeds, the water rust on the surface of the steel wire is dissolved in the treatment liquid, and the Fe ³⁺ concentration in the treatment liquid increases. The Fe ³⁺ concentration is measured, for example, by a titration method using an ethylenediaminetetraacetic acid solution. When the concentration exceeds 1000 mg / L, the treatment liquid is replaced.

  The oxidation-reduction potential of the treatment liquid during the water rust removal treatment is adjusted to 510 mV or less, preferably 460 mV or less, more preferably 410 mV or less with respect to the hydrogen standard electrode potential. The redox potential is adjusted by, for example, adding sodium L-ascorbate and air bubbling.

  The higher the concentration of the organic chelating agent and the higher the temperature of the treatment liquid, the shorter the time required to remove water rust. On the other hand, if it is immersed for a long time in the process liquid containing a high concentration organic chelating agent, a metal will be corroded. Therefore, it is necessary to appropriately set the immersion time of the steel wire according to the concentration of the organic chelating agent during the treatment and the temperature of the treatment liquid.

A steel wire was immersed in a treatment liquid containing ethylenediaminetetraacetic acid potassium salt as an organic chelating agent, and the relationship among the concentration, pH, treatment temperature, and treatment time of the organic chelating agent was investigated. Table 2 shows the processing conditions. As a sample, a work in which 10 wires (material: S-45C, average diameter: 15 mm, length: 10 cm) are bundled with yarn is used, and acid treatment is performed under the conditions using hydrochloric acid shown in Table 1. , Washed with water. The pH was adjusted by adding potassium hydroxide. Fe ²⁺ and Fe ³⁺ were adjusted by adding ferrous chloride and ferric chloride (FeCl ₃ ), respectively. The oxidation-reduction potential was measured using a 3.3 mol / L silver-silver chloride electrode, and sodium L-ascorbate was added to adjust the value of the oxidation-reduction potential.

The concentration (active ingredient concentration) of the organic chelating agent (ethylenediaminetetraacetic acid potassium salt) in the treatment liquid was measured by the following procedure.
(Organic chelating agent active ingredient concentration measurement method)
(1) Collect 5 ml of the treatment solution with a whole pipette and place it in a 300 ml Erlenmeyer flask or beaker.
(2) Add 100 ml of distilled water or ion exchange water to dilute the treatment solution.
(3) Add 10 ml of pH 9 borate buffer solution (commercially available product or diluted 5 g of hydrous borax in 1 L of distilled water).
(4) Add a small amount of murexide diluted powder as an indicator.
(5) Titrate with 1/40 M copper sulfate aqueous solution. The titration is finished when the color changes from purple to purple. The organic chelating agent concentration is calculated according to the formula (1).
Organic chelating agent concentration (mg / L) = 0.128 × copper sulfate aqueous solution dropping amount (ml) (1)

  In FIG. 1 to FIG. 6, the treatment liquid temperature when water rust removal is performed using treatment liquids having pH of 4.0, 4.5, 5.0, 8.0, 8.5, and 9.0, respectively. The graph showing the relationship between processing time is shown. In the figure, the horizontal axis represents the treatment liquid temperature and the vertical axis represents the treatment time. The treatment time was set to the minimum immersion time when the appearance of the sample after treatment was visually observed and the appearance was clean and the weight loss was 0.1% or less.

In any case, the treatment time was shortened as the treatment solution temperature was increased and the organic chelating agent concentration was increased. Further, at the same organic chelating agent concentration and treatment solution temperature, the treatment time tended to be shorter as the pH was lower.
In the case of pH 5.0 or less, the metal was corroded when immersed in a treatment solution having an organic chelating agent concentration of 200 g / L or more for a long time (weight reduction was greater than 0.1%). When the pH was 5.0 or more, water rust could not be removed with a treatment liquid having an organic chelating agent concentration of 1 g / L.

The influence of the Fe ²⁺ concentration in the treatment liquid was investigated. As a sample, a work in which 10 wires (material: S-45C, average diameter: 15 mm, length: 10 cm) are bundled with yarn is used, and acid treatment is performed under the conditions using hydrochloric acid shown in Table 1. , Washed with water. Ethylenediaminetetraacetic acid was used as the organic chelating agent, and the concentration of the organic chelating agent was 50 g / L. It adjusted by adding potassium hydroxide so that it might become pH 5.0. The amount of the treatment liquid was 500 ml, and the treatment liquid temperature was 20 ° C. Ferrous chloride was added to the treatment liquid as Fe ²⁺ . Fe ²⁺ concentration and Fe ³⁺ concentration were measured by the titration method described below. A 3.3 mol / L silver-silver chloride electrode was used to measure the oxidation-reduction potential of the treatment liquid.

(Fe ³⁺ concentration measurement method)
(1) Collect 2 ml of the processing solution as a sample.
(2) Add 10 ml of 20% aluminum sulfate aqueous solution (20 g of aluminum sulfate 14-18 hydrate dissolved in water to make the total amount 100 ml).
(3) 20 ml of a pH buffer solution (10.7 g of ammonium chloride and 20 ml of 99.7% acetic acid dissolved in water to make the total volume 1000 ml) is added.
(4) Add 2 ml of 10% sulfosalicylic acid solution (10 g of sulfosalicylic acid dihydrate dissolved in water to make the total amount 100 ml). If Fe ³⁺ is present, it turns reddish purple at this point.
(5) Warm the above solution to 40 ° C. and titrate with 0.1 M ethylenediaminetetraacetic acid (EDTA). The titration is finished when the color changes from reddish purple to tan. The Fe ³⁺ concentration is calculated from equation (2).
Fe ³⁺ concentration (ppm) = EDTA drop amount (ml) × 5.585 × 500 × F (2)
Here, F represents a factor of 0.1 M ethylenediaminetetraacetic acid.

(Fe ²⁺ concentration measurement method)
(1) About 2 g of ammonium persulfate (ammonium peroxodisulfate) is added to the liquid ^{subjected to the} above-described Fe ³⁺ concentration measurement operation. At this time, it turns reddish purple.
(2) Warm the above solution to 40 ° C. and titrate with 0.1 M ethylenediaminetetraacetic acid solution. The titration is finished when the color changes from reddish purple to tan. The Fe ²⁺ concentration is calculated from equation (3).
Fe ²⁺ concentration (ppm) = EDTA drop amount (ml) × 5.585 × 500 × F (3)
Here, F represents a factor of 0.1 M ethylenediaminetetraacetic acid.

After immersing for 120 seconds in each treatment solution with different Fe ²⁺ concentrations, the appearance of the steel wire was visually observed to evaluate the degree of water rust removal. Table 3 shows the results.

When the Fe ²⁺ concentration was less than 10 mg / L, the redox potential was high and the reducing power was weak, so that the amount of residual water rust after treatment was large. When the Fe ²⁺ concentration was 10 mg / L or more, water rust could be almost removed, and when the Fe ²⁺ concentration was 50 mg / L or more, water rust could be completely removed.

The influence of the Fe ³⁺ concentration in the treatment liquid was investigated. As a sample, a work in which 10 wires (material: S-45C, average diameter: 15 mm, length: 10 cm) are bundled with yarn is used, and acid treatment is performed under the conditions using hydrochloric acid shown in Table 1. , Washed with water. Ethylenediaminetetraacetic acid was used as the organic chelating agent, and the concentration of the organic chelating agent was 50 g / L. It adjusted by adding potassium hydroxide so that it might become pH 5.0. The amount of the treatment liquid was 500 ml, and the treatment liquid temperature was 20 ° C. Ferrous chloride was added to the treatment solution so that the Fe ²⁺ concentration was 100 mg / L. Ferric chloride was added as Fe ³⁺ . The Fe ²⁺ concentration and the Fe ³⁺ concentration were measured by the method described above. A 3.3 mol / L silver-silver chloride electrode was used to measure the oxidation-reduction potential of the treatment liquid.

After immersing for 120 seconds in each treatment solution with different Fe ³⁺ concentrations, the appearance of the steel wire was visually observed to evaluate the degree of water rust removal. Table 4 shows the results.

When the Fe ³⁺ concentration was 1500 mg / L or more, the oxidation / reduction potential was increased due to the oxidation action of Fe ³⁺ and the reduction power was weakened. In addition, the ingot of the steel wire rod was corroded by the oxidizing action of Fe ³⁺ . For this reason, it is anticipated that the number of disconnections during wire drawing will increase significantly. When the Fe ³⁺ concentration was 1000 mg / L or less, water rust on the steel wire surface could be almost removed, and water rust could be reliably removed at 500 mg / L or less.

The influence of the oxidation-reduction potential of the treatment liquid during the water rust removal treatment was investigated. As a sample, a work in which 10 wires (material: S-45C, average diameter: 15 mm, length: 10 cm) are bundled with yarn is used, and acid treatment is performed under the conditions using hydrochloric acid shown in Table 1. , Washed with water. Ethylenediaminetetraacetic acid was used as the organic chelating agent, and the concentration of the organic chelating agent was 50 g / L. It adjusted by adding potassium hydroxide so that it might become pH 5.0. The amount of the treatment liquid was 500 ml, and the treatment liquid temperature was 20 ° C. Ferrous chloride was added to the treatment solution so that the Fe ²⁺ concentration was 100 mg / L. The Fe ³⁺ concentration was 0 mg / L. The oxidation-reduction potential was measured using a 3.3 mol / L silver-silver chloride electrode, and the value of the oxidation-reduction potential was adjusted by addition of sodium L-ascorbate and air bubbling.

  The steel wire was immersed for 120 seconds in each treatment solution having a different oxidation-reduction potential. The appearance of the steel wire after immersion was visually observed to evaluate the degree of water rust removal. Table 5 shows the results. Water rust could be almost removed when the oxidation-reduction potential (vsSHE) was 510 mV or less, and it could be reliably removed at 460 mV or less.

The rust prevention performance after the water rust removal treatment when a surface treatment agent to which a surfactant or glycol solvent was added was used for the treatment was investigated. As a sample, a work in which 10 wires (material: S-45C, average diameter: 15 mm, length: 10 cm) were bundled with a thread was used.
The sample was immersed in a 10 wt% hydrochloric acid aqueous solution for 5 minutes to perform pickling treatment, and then immersed in tap water for 2 minutes to perform water washing treatment. Then, the sample was left still for 2 minutes at room temperature, and water rust was generated on the sample surface. A sample in which water rust was generated was immersed in the treatment liquid 1 to treatment liquid 3 shown in Table 6 to perform a water rust removal treatment, and left at room temperature.

  In the sample subjected to the water rust removal treatment with the treatment liquid 1, generation of oxide scale was confirmed on the sample surface about 5 hours after the treatment. On the other hand, in the samples subjected to the water rust removal treatment with the treatment liquid 2 (surfactant addition) or the treatment liquid 3 (glycol solvent addition), generation of oxide scale was not confirmed even after 35 hours from the treatment. Thus, the rust prevention performance after the water rust removal process was able to be improved by adding surfactant or a glycol-type solvent in a process liquid.

<Surface film treatment process>
A surface film is formed on the surface of the steel wire from which water rust has been removed by the water rust removal process using a surface film treatment agent. The surface film treatment agent provides the following actions.
(1) A film is formed on the surface of the steel wire, and the lubricant is transported between the steel wire and the die during the wire drawing process. At the same time, it is mixed with a lubricant to improve lubricity.
(2) Appropriate amount remains on the surface of the steel wire after drawing to improve the lubricity during forming.
(3) Neutralize the acid solution adhering to the wire surface during the pickling step.
(4) Rust (oxidized scale) generation on the surface of the wire is prevented before the wire drawing process.

In general, a lime soap treatment solution or a phosphate treatment solution is used as the surface film treatment agent. When performing a water rust removal process using the surface treating agent of the component demonstrated in the water rust removal process, a lime soap treatment liquid is used. When the phosphating solution is used, the organic chelating agent remaining on the steel wire surface is mixed into the phosphating solution. For this reason, surface treatment property is inhibited, for example, a phosphate (zinc phosphate) film is not formed on the steel wire surface. When a lime soap treatment liquid is used, the organic chelating agent is mixed, so that the dispersibility of soap lime is improved, and as a result, the surface treatment performance is improved, which is preferable.
In this embodiment, a steel wire is immersed in a lime soap treatment solution having a concentration of 5 to 15% and a temperature of 30 to 80 ° C., and surface coating is performed.

<Dry wire drawing process>
After forming the surface film, wire drawing is performed. The basic components of the lubricant used in dry drawing are powdered metal soaps and inorganic substances. The general blending ratio is 50 to 80% for metal soaps and 20 to 50% for inorganic substances. On the other hand, several percent of additives are added.
In this embodiment, the surface treatment agent and the water rust removal step reliably remove the water rust on the surface of the steel wire, and suppress the generation of oxide scale after the water rust removal step. Therefore, damage to the die can be reduced during wire drawing, and the die life can be extended. Moreover, there is little corrosion of a metal | base metal and the frequency | count of disconnection at the time of wire drawing can be reduced significantly.

  The steel wire that has been subjected to the surface treatment in the above-described procedure using the surface treatment agent of the present embodiment, the surface is not excessively dissolved, the water rust on the surface of the wire is reliably removed, and the oxide scale after water rust removal Is suppressed. Therefore, the steel wire rod is excellent in aesthetic appearance. Moreover, since the surface treating agent of this embodiment does not contain phosphorus, the delayed fracture due to immersion phosphorus does not occur in the steel wire material that has been subjected to the water rust removal treatment of this embodiment.

  A wire drawing pretreatment of a steel wire (material: S-45C, average diameter: 15 mm) was performed. One wire processing weight was set to 2t.

  The acid cleaning conditions were 10 wt% sulfuric acid, a temperature of 60 ° C., a treatment time of 1200 seconds, and an iron concentration in the liquid of 500 g / L or less. Water rust removal was performed by immersing the steel wire in a treatment solution containing ethylenediaminetetraacetic acid as an organic chelating agent (conditions at the start of treatment are shown in Table 7) for 60 seconds. Until the organic chelating agent concentration during the water rust removal treatment was less than 1 g / L, the organic chelating agent was continuously used without being added. The surface film treatment conditions were such that the concentration of the lime soap treatment solution was 10 wt% and the temperature was 60 ° C.

FIG. 7 shows the relationship between the total iron concentration (Fe ²⁺ concentration + Fe ³⁺ concentration) and the organic chelating agent concentration in the water rust removal treatment liquid from the start of the treatment. In the figure, the horizontal axis represents the total iron concentration and the vertical axis represents the organic chelating agent concentration. In FIG. 8, the relationship between the total iron density | concentration in a water rust removal processing liquid and a wire processing amount is shown. In the figure, the horizontal axis represents the amount of wire rod treated and the vertical axis represents the total iron concentration. Treatment reduced the organic chelating agent concentration and increased the iron concentration accordingly. When the concentration of the organic chelating agent at the start of the treatment was 58 mg / L, the treatment liquid could be used up to a steel wire treatment amount of 2090 t (total iron concentration of 2080 ppm).

  After the removal of water rust, the appearance of the steel wire material that has been subjected to the surface film treatment and the dry wire drawing treatment is excellent in appearance without coloring due to water rust. On the other hand, the wire that was drawn without performing the water rust removal treatment was colored by water rust remaining on the surface.

It is a graph showing the relationship between the process liquid temperature at the time of performing water rust removal using the process liquid of pH 4.0, and process time. It is a graph showing the relationship between the process liquid temperature at the time of performing water rust removal using the process liquid of pH4.5, and process time. It is a graph showing the relationship between the process liquid temperature at the time of performing water rust removal using the process liquid of pH5.0, and process time. It is a graph showing the relationship between the process liquid temperature at the time of performing water rust removal using the process liquid of pH 8.0, and process time. It is a graph showing the relationship between the process liquid temperature at the time of performing water rust removal using the process liquid of pH8.5, and process time. It is a graph showing the relationship between the process liquid temperature at the time of performing water rust removal using the process liquid of pH 9.0, and process time. It is a graph showing the relationship between the total iron density | concentration in the process liquid after a process start, and an organic chelating agent density | concentration. It is a graph showing the relationship between the total iron concentration in a process liquid, and a wire processing amount.

Claims (10)

  One or more organic chelating agents selected from aminocarboxylic acids and aminocarboxylic acid salts are contained, the concentration of the organic chelating agent is 1 g / L or more and 300 g / L or less, and the pH is 4.0 or more and 9.0. A surface treatment agent comprising an aqueous solution prepared as follows.   The surface treatment agent according to claim 1, wherein the aqueous solution contains a surfactant or a glycol solvent. A step of immersing carbon steel in a treatment liquid in which Fe ²⁺ is added to a surface treatment agent comprising an aqueous solution containing one or more organic chelating agents selected from aminocarboxylic acids and aminocarboxylates;
The pH of the treatment liquid, the concentration of the organic chelating agent in the treatment liquid, the concentration of Fe ^{2+ in} the treatment liquid, the Fe ³⁺ concentration in the treatment liquid, and the oxidation-reduction potential of the treatment liquid. And a step of adjusting the surface.   The surface treatment method according to claim 3, wherein the pH of the treatment liquid is adjusted to a range of 4.0 or more and 9.0 or less.   The surface treatment method of Claim 3 which adjusts the density | concentration of the said organic chelating agent in the range of 1 g / L or more and 300 g / L or less. The surface treatment method according to claim 3, wherein the concentration of Fe ²⁺ is adjusted to 10 mg / L or more. The surface treatment method according to claim 3, wherein the concentration of Fe ³⁺ is adjusted to 1000 mg / L or less.   The surface treatment method according to claim 3, wherein the oxidation-reduction potential is adjusted to 510 mV or less with respect to a hydrogen standard electrode potential.   The surface treatment method according to claim 3, wherein the aqueous solution contains a surfactant or a glycol solvent. It is immersed in a treatment solution in which Fe ²⁺ is added to an aqueous solution containing one or more organic chelating agents selected from aminocarboxylic acids and aminocarboxylates, and the pH of the treatment solution and the organic chelating agent in the treatment solution Carbon steel whose surface has been treated by adjusting the concentration of Fe, the concentration of Fe ^{2+ in} the treatment liquid, the Fe ³⁺ concentration in the treatment liquid, and the oxidation-reduction potential of the treatment liquid.

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